Leetcode: Letter Combinations of a Phone Number
2015-09-09 09:16
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Question
Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below.
Input:Digit string “23”
Output: [“ad”, “ae”, “af”, “bd”, “be”, “bf”, “cd”, “ce”, “cf”].
Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.
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Solution
[code]class Solution(object): def letterCombinations(self, digits): """ :type digits: str :rtype: List[str] """ self.dict = {'2':['a','b','c'], '3':['d','e','f'], '4':['g','h','i'], '5':['j','k','l'], '6':['m','n','o'], '7':['p','q','r','s'], '8':['t','u','v'], '9':['w','x','y','z'] } res = [] if digits=='' or len(digits)==0: return res self.helper(digits, 0,'',res) return res def helper(self, digits, num, string, res): if num==len(digits): res.append(string) return for letter in self.dict[digits[num]]: self.helper(digits, num+1, string+letter, res)
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